 |
 |
Hi Jillian, By dividing the volume by the number of voxels per resel you'll get the number of resels in your search space (ie the brain mask used in the 3rd level analysis). If you then use ptoz 0.05 -g RESELS_COUNT you'll get the voxel-wise height threshold necessary for a p-value of 0.05 in a GRF of the volume (in resels) of your data set. In other words, any voxel with a z-score equal to or higher than the output of that command reaches a corrected level of significance in your experiment. There is no additional extent threshold. So yes, it is considerably more conservative than an uncorrected p<0.05. On the other hand, it appropriately takes into account the number of independent comparisons being made. Hope this helps. Joe ------------------ Joseph T. Devlin, Ph. D. Dept. of Psychology, UCL Gower Street London, WC1E 6BT, UK email: [log in to unmask]